feat(session/gamestream): the compat plane learns a game's lifetime too

Moonlight sessions had neither direction of the session⇄game binding: a game
exiting left the player looking at a desktop, and a session ending never touched
the game. The machinery for both landed with the native plane; this wires it up.

The compat plane had no way to say "this is over" — RTSP carries no close code —
so `/cancel`, the management stop and a game exiting all looked exactly like a
client vanishing. They now set a session quit flag, which is what lets the
virtual display skip its keep-alive linger for a real stop and what the
end-game-on-session-end policy reads to tell a decision from a network blip. A
drop still lingers, and still gets its reconnect window.

Moonlight can't resume a session, so a client coming back for a game it left
behind does it by launching the title again — that reclaims the waiting game
before anything starts, rather than letting the old window close on the copy the
player is now holding.

Both planes now resolve a launch through one lookup (`resolve_launch`), so a
GameStream title arrives with the same identity and the same detect signals a
native one does; `resolve_session_launch`/`launch_command` were the older,
identity-less half of that and are gone. A Moonlight game also has no
live-session entry to hang off, so the status surface gains a slot for it —
without it the Dashboard would show a stream with no game while one was running.

Gates on .21: check + clippy --all-targets clean, 296 tests (293 + 3), fmt
CI-parity.

crates/punktfunk-host/src/mgmt/session.rs

@@ -22,7 +22,7 @@ use std::sync::atomic::Ordering;
     )
 )]
 pub(crate) async fn stop_session(State(st): State<Arc<MgmtState>>) -> StatusCode {
-    let was_streaming = st.app.end_session("management API stop");
+    let was_streaming = st.app.quit_session("management API stop");
     // Native plane: the GameStream teardown above doesn't reach it (it runs its own loops off the shared
     // session registry), so signal every live native session to tear down too.
     let native = crate::session_status::count();